Pleated filter and mechanism for forming same



2 Sheets-Sheet 1 1N VENTO/e5 A 7' TOR/VEV May 17,1960 L. G. ALLEN x-:TAL

PLEATED FILTER AND MECHANISM FOR FORMING SAME Filed Oct. 23. 1957 May 17, 1960 l.. G. ALLEN ETAL PLEATED FILTER AND MECHANISM FOR FORMING SAME Filed OCT.. 23, 1957 2 Sheets-Sheet 2 IgM/f fr y www Andhra.,

UnitedY States Patent 'PLEATED mTER ANDlvntcHANlsMiloilV lronlsiiNGSAME f Lloyd G. Allen and nomma. McMillan, seglnew, YMich., assignors to General MotorsCorporation, .Def "troit,'Mich., a corporation Vof Delaware Application October 23, 1957, Serial No. 691,992 s yzeclalms. (cities-vif y 'The invention `relates toa filter unit-for filtering: fluids and the mechanism for forming .the lter element.: The f l several pleats would inadvertently be left close" together and full filter capacity would not be realized. It is now proposed to provide means for spacing each pleat of a filter element at a predetermined distance relative to the adjacent pleat without the necessity of manually positioning the pleats during installation of the element in the end walls. The invention also provides for the proper radius of curvature of the pleated element-when installed to provide an annular filter unit. These results are 'gained by forming bumps or dimples onathe pleats inoppositely disposed relationship so that adjacent bumps on adjacent pleats engage Yeach other. A greater radius of curvature lCC iatented May 17, 1960 wedge shaped in cross section and terminate with a relatively small radius of curvature at their outer ends34.,

The paddles 32 are also generally wedge'shapedin cross section. They may terminate in a somewhat. larger radius of .curvature at their outer ends 36. The filter .element V20 is thusformedto have one side of the pleated strip provided with folds having a larger radius of curvature thanthe otherside. The side with the larger radius of curvaturebecomes the outerperiphery 38 of the filter ele,- ment 20 when it is installed as part of annular filter .unit 10. The. inner periphery 40 of the filter-element includes `the folds having the smaller radius of curvature. The

difference in radii of curvature causes the element .20,V

when placed in position.intermediatescreensl and 18, to assumethe proper radius of curvature for the Yannular'.

unit ofwhich it .becomes a part. It may alsobe desirable to. have the folds formedlwith the sam-e radii of curvature for certain apjgilicationsy such as planarlters,` or to have the smaller radiusfoldon the outercurvefjand the larger radiusfold ofthe inner curve of a curvedfilter. Y

.Eachpleatincludes twoV sides 42 and 4 4'interc'onne`cted byr an outer periphery fold 46 and connected tothe sides, ofi-,adjacent pleatsby inner.y periphery folds 48. Eachof thepleat/sides 42 and 44,is.deformed to provide one Yor. more bumps 50 adjacent the outer fold 46. Three such bumpsareshown on the filter element illustrated. The

. bumps may be spherically formed or have other desirable configurations. They may be in rows or otherwise spaced. Each pleat side may also be provided with one orA more dimples 52 adjacent the inner fold 148.'- The'v dirliples 52 ar similar to the bumps 50, but are depressed inwardly of the pleat. This construction permits adjacent bumps S0 to engage each other and maintain a constant spacing between adjacent pleat sides. Theinner sides of.- dimples 52 also constitute bumps which similarlyengage each other to maintain a constant spacing between'adjacent pleat sides at the inner periphery of thefilter element: While it is preferable to provide bumps 50 and of the pleat fold at its outer edge as comparedv to the radius of curvature of the pleat fold at the inner edge as utilized to provide the approximate overall radius of curvature desired.

In the drawings:

Fig. l illustrates e vliner unil having e pleated alter embodying the invention, with parts in section;

Fig. 2 is a cross section view of a portion of the filter unit of Fig. 1 and is taken in ythe direction of arrows 2 on that figure; e

Fig. 3 is an elevational view having parts broken away and taken in the direction of arrows 3-3 of Fig. 2;

Fig. 4 is an elevational' view having parts broken away andV taken in the direction of arrows 4-'4 of Fig'.- 2; and

Fig. 5 is an enlarged cross section view of the filter element during process of manufacture and including mechanism for forming the filter element. v

The filter unit 10 embodying the invention may be o the disposable type and is illustrated inthedrawings as an air filter unit such as those used to' filter the intake air of an internal combustion engine. The unit is comprised of a pair of spaced annular end wallsor supports 12 and 14, inner and outer walls of wire screens 16 and 18, and a pleated filter element 20. The ends 22, 24,v 26 and 28 of screens 16 and 18 may be embedded in the end walls 12 and 14 to anchor thescreens securely.

The filter element 20 is formed from a strip of suitable filter material by means of intermeshing folding paddles 30 and 32. The strip of filter material being folded and formed is received intermediate the meshed paddles. The strip assumes the contour of the paddles and is pleated to form the desired configuration. This is best seen in Figure 5. The padd1es30 are generally dimples 52, a filter element may be made with only one type of such deformation to obtain some advantages inherent in the invention. j e l Paddles 30 are provided with passages 54 and protuberances 56. Paddles 32 are similarly provided with passages 58 and protuberances 60. The passages 54 and protuberances 60 are aligned when paddles 30 and 32 are fullygmeshed. Protuberances `60 thus force portions of the filter element 20 into passages 54 to form bumps 50. Protuberances 56 and passages` -58 are similarly aligned to form dimples 52. e y

As is readily seen in Fig. 2, each of the pleats Iof the filter element 20 are equally spaced when assembled to form a filter unit. 'This results in arl increase in filtering capacity as comparedV to filters having unequal spacing. All of the pleat sides are exposed to air passing through the filterand full advantage is taken of the entire area of the filter element. The use of the maximum area determines filter capacity to a great extent since the particles being filtered are held in the filter body.` If any surfaces Y*of the filter element 20 areunexposed or only t foreign matter lto its full capacity before other portions a filter. element without changing its overall dimensions. This additional material provides greater filtering capacity not realized by prior elements.

' Filter units are usually built up by placing the filter i element between the supporting screens and on the lower endwall. When filter elements without spacing bumps or dimples are used, an operator must adjust the element pleats Auntil an acceptable spacing is obtained. When a filter element embodying the invention is used, the pleats are self `spacing and no individual attention need be given at this point. Y

' `What is claimedris:

1. An annular filter unit comprising, parallel spaced annular end walls, an inner peripheral screen and an outer peripheral screen connecting said end walls to form an annular chamber, andra pleated annular filter element mounted in said chamber, said filter element having radially extending pleats in evenly spaced relation, said pleats each comprising two sides and, an arcuate interconnecting fold and being interconnected with one side of each adjacent pleat by an arcuate connecting fold, a series ofoutinwardly disposed dimples forming inwardly projecting bumps, saidinwardly projecting bumps providing theonly common contaetpoints between the two sidesY of each of said pleats,"said` interconnectingv folds having a larger radius of curvature than said connecting folds.v

wardly e'xtending'bumps being formed outwardly from dially extending pleats in evenly spaced relation, said y ReferencesCitedin file ofvthis patent i UNITED STATES PATENTS 1,967,726 s. Sherman July 24, 1934 2,290,608' j EvansY *July 21, 1942` 2,771,156 Kasten etal Nov. 20, 1956 2,824,622 Buckman'; vFeb. 25, 1958 2,836,302 Buckman' May 27, 1958 FOREIGN PATENTS 745,466 France Feb. 21, 1933` 817,369 France Feb. 4, 1937 1,111,568 France Nov. 2, 1955Y 295,379 V Switzerland ..1 Dec, 3l, 

